• Title/Summary/Keyword: Delamination length

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Detection of Delamination inside Concrete Using Ground Penetrating Radar (GPR을 이용한 콘크리트 내 공동 탐사)

  • Rhim, Hong-Chul;Lee, Soong-Jae;Woo, Sang-Kyun;Song, Young-Chul
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.7 no.2
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    • pp.177-184
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    • 2003
  • A series of experimental work has been conducted to evaluate the capability of Ground Penetrating Radar (GPR) system in detecting delamination inside concrete. Three antenna at 900 MHz, 1000 MHz, and 1500 MHz frequency are used in the experiments for laboratory size specimens, and 400 MHz antenna has been used for a large size specimen. The laboratory size specimens have the dimensions of 1,000 mm (length) ${\times}$ 600 mm (width) ${\times}$ 140 mm (thickness) with a delamination of 200 mm (length) ${\times}$ 600 mm (width) ${\times}$ 140 mm (thickness). The cover depth of the delamination is varied as follows: 20 mm, 30 mm, 60 mm, and 70 mm. In all cases, the delamination has been successfully identified. The property of three frequencies was seized about detecting delamination. Also, it was shown that the image results in GPR were improved by signal processing.

Failure Mode and Flexural Performance of RC Beams Strengthened with Different Bond Length of CFRP Strips (탄소섬유판으로 보강된 RC부재의 부착길이 변화에 따른 파괴모드 및 휨 보강성능)

  • Choi, Ki-Sun;You, Young-Chan;Kim, Keung-Hwan
    • Proceedings of the Korea Concrete Institute Conference
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    • 2006.11a
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    • pp.173-176
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    • 2006
  • The one of the commonly reported failure mode of the RC beam strengthened with FRP was caused by the separation of the concrete cover, so called delamination. Therefore, ACI440 recommended that concrete cover delamination can be prevented in strengthened beams if bond length of FRP composite be exteneded over a point of cracking moment. In this study, the failure mode and the flexural performance of RC beam with different bond length of FRP are estimated. Each bonded length is calculated based on the point of cracking moment with addition or subtraction of specific length(=150mm). The results of this study show that mid-span debonding occurs in the specimen strengthened with CFRP strips which are bonded over the point of cracking moment, while concrete cover deliamination occurs at the termination point of CFRP in the specimen with less bonded length than the point of cracking moment region.

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A prediction of the thermal fatigue life of solder joint in IC package for surface mount (표면실장용 IC 패키지 솔더접합부의 열피로 수명 예측)

  • 윤준호;신영의
    • Journal of Welding and Joining
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    • v.16 no.4
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    • pp.92-97
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    • 1998
  • Because of the low melting temperature of solder, each temperature cycle initiates an irrecoverable creep deformation at the solder interconnection which connects the package body with the PCB. The crack starts and propagates from the position where the creep deformation is maximized. This work has tried to compare and analyze the thermal fatigue life of solder interconnection which is affected by the lead material, the size of die pad, chip thickness, and interface delamination of 48-Pin TSOP under the temperature cycle ($0^{\circ}C$~1$25^{\circ}C$). The crack initiation position and thermal fatigue life which are calculated by using FEA method are well matched with the results of experiments. The thermal Fatigue life of copper lead frame is extended around 3.6 times longer than that of alloy 42 lead frame. It is maximized when the chip size is matched with the length of the lead. It tends to be extended as the thickness of chip got thinner. As the interfacial delamination between die pad and EMC is increased, the thermal fatigue life tends to decrease in the beginning of delamination, and increase after the delamination grew after 45% of the length of die pad.

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Enhancement of delamination strength in Cu-stabilized coated conductor tapes through additional treatments under transverse tension at room temperature

  • Shin, Hyung-Seop;Bautista, Zhierwinjay;Moon, Seung-Hyun;Lee, Jae-Hun;Mean, Byoung-Jean
    • Progress in Superconductivity and Cryogenics
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    • v.19 no.2
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    • pp.25-28
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    • 2017
  • In superconducting coil applications particularly in wet wound coils, coated conductor (CC) tapes are subjected to different type of stresses that could affect its electromechanical transport property. These include hoop stress acting along the length of the CC tape and the Lorentz force acting perpendicular to the CC tape's surface. Since the latter is commonly associated with the delamination problem of multi-layered REBCO CC tapes, more understanding and attention on the delamination phenomena induced in the case of coil applications are needed. Difference on the coefficient of thermal expansion (CTE) of each constituent layer of the CC tape, the bobbin, and the impregnating materials is the main causes of delamination in CC tapes when subjected to thermal and mechanical cycling. In the design of degradation-free superconducting coils, therefore, characterization of the delamination behaviors including mechanism and strength in the multi-layered REBCO CC tapes becomes a critical issue. Various trials to increase the delamination strength by improving interface characteristics at interlayers have been performed. In this study, in order to investigate the influences of laser cleaning and Ag annealing treated at the substrate side surface, transverse tensile tests were conducted under different sample configurations using $4.5mm{\times}8mm$ upper anvil. The mechanical delamination strength of differently processed CC samples was examined at room temperature (RT). As a result, the Sample 1 with the additional laser cleaning and Ag annealing processes and the Sample 2 with additional Ag annealing process only showed higher mechanical delamination strength as compared to the Sample 3 without such additional treatments. Sample 3 showed quite different behavior when the loading direction is to the substrate side where the delamination strength much lower as compared to other cases.

Analysis of natural frequencies of delaminated composite beams based on finite element method

  • Krawczuk, M.;Ostachowicz, W.;Zak, A.
    • Structural Engineering and Mechanics
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    • v.4 no.3
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    • pp.243-255
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    • 1996
  • This paper presents a model of a layered, delaminated composite beam. The beam is modelled by beam finite elements, and the delamination is modelled by additional boundary conditions. In the present study, the laminated beam contains only one delaminated region through the thickness direction which extends to the full width of the beam. It is also assumed that the delamination is open. The influence of the delamination length and position upon changes in the bending natural frequencies of the composite laminated cantilever beam is investigated.

Analyses of Fracture Parameters and Prediction of Crack Propagation Path on Delamination in the LSI Package (반도체 패키지의 층간박리 파괴역학인자 해석 및 균열진전경로 예측)

  • Chung, Nam-Yong;Park, Cheol-Hee
    • Journal of the Korean Society of Manufacturing Technology Engineers
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    • v.18 no.4
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    • pp.401-409
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    • 2009
  • This paper presents a method of calculating the stress intensity factor (K) and crack propagation direction (${\theta}_0$) at the crack-tip that is associated with delamination in the large scale integration(LSI) package. To establish a reasonable strength evaluation method and life prediction, it is necessary to assess fracture parameters under various fracture conditions. Therefore, we conducted quantitative stress singularity analysis considering thermal stress simulating the changes of crack length (a), (h) and (v) in delamination using the 2-dimensional elastic boundary element method (BEM), and from these results predicted crack propagation direction and path.

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Analysis of the strain energy release rate for time-dependent delamination in multilayered beams with creep

  • Rizov, Victor I.
    • Advances in materials Research
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    • v.11 no.1
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    • pp.41-57
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    • 2022
  • This paper is focused on delamination analysis of a multilayered inhomogeneous viscoelastic beam subjected to linear creep under constant applied stress. The viscoelastic model that is used to treat the creep consists of consecutively connected units. Each unit consists of one spring and two dashpots. The number of units in the model is arbitrary. The modulus of elasticity of the spring in each unit changes with time. Besides, the modulii of elasticity and the coefficients of viscosity change continuously along the thickness, width and length in each layer since the material is continuously inhomogeneous in each layer of the beam. A time-dependent solution to the strain energy release rate for the delamination is derived. A time-dependent solution to the J-integral is derived too. A parametric analysis of the strain energy release rate is carried-out by applying the solution derived. The influence of various factors such as creep, material inhomogeneity, the change of the modulii of elasticity with time and the number of units in the viscoelastic model on the strain energy release rate are clarified.

Delamination Detection of FRP Sheet Reinforced Concrete Using Microstrip Patch Antenna (Microstrip Patch Antenna를 이용한 탄소섬유시트 보강콘크리트의 박리 탐사)

  • Rhim, Hong-Chul;Lee, Hyo-Seok;Woo, Sang-Kyun;Song, Young-Chul
    • Journal of the Korean Society for Nondestructive Testing
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    • v.27 no.2
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    • pp.134-141
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    • 2007
  • A series of experimental work has been conducted to evaluate the capability of microstrip patch antenna system in detecting delamination in fiber reinforced Plastic (FRP) sheet reinforced concrete. For that purpose, a prototype microstrip patch antenna was developed with 15 GHz center frequency and 1 GHz bandwidth. For the comparison, a horn antenna with 15 GHz center frequency and 10 GHz bandwidth was used for the measurements of the same specimens. The laboratory sire specimens have the dimensions of 600 mm (length) $\times$ 600 mm (width) $\times$ 50mm (thickness) with a series of delaminations of 300 mm (length) $\times$ 300mm (width) $\times$ 5, 10, 15 mm (thickness). FRP of 1.5 mm thickness and epoxy of 3 mm thickness were placed on the top of artificially created delamination to represent actual FRP reinforced concrete condition. In all cases, the delamination has deen successfully identified. Also, it was shown that imaging results in microstrip patch antenna were improved by signal processing.

Delamination behaviors of GdBCO CC tapes under different transverse loading conditions

  • Gorospe, Alking B.;Bautista, Zhierwinjay M.;Shin, Hyung-Seop
    • Progress in Superconductivity and Cryogenics
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    • v.17 no.3
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    • pp.13-17
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    • 2015
  • In superconducting coil applications particularly in wet wound coils, coated conductor (CC) tapes are subjected to different type of stresses. These include hoop stress acting along the length of the CC tape and the Lorentz force acting perpendicular to the CC tape's surface. Since the latter is commonly associated with delamination problem of multi-layered CC tapes, more understanding and attention on the delamination phenomena induced in the case of coil applications are needed. Difference on the coefficient of thermal expansion (CTE) of each constituent layer of the CC tape, the bobbin, and the impregnating materials is the main causes of delamination in CC tapes when subjected to thermal cycling. The CC tape might also experience cyclic loading due to the energizing scheme (on - off) during operation. In the design of degradation-free superconducting coils, therefore, characterization of the delamination behaviors including mechanism and strength in REBCO CC tapes becomes critical. In this study, transverse tensile tests were conducted under different loading conditions using different size of upper anvils on the GdBCO CC tapes. The mechanical and electromechanical delamination strength behaviors of the CC tapes under transverse tensile loading were examined and a two-parameter Weibull distribution analysis was conducted in statistical aspects. As a result, the CC tape showed similar range of mechanical delamination strength regardless of cross-head speed adopted. On the other hand, cyclic loading might have affected the CC tape in both upper anvil sizes adopted.

Delamination behavior of multidirectional laminates under the mode I loading (모드 I 하중조건하에 있는 다방향 적층 복합재료의 층간파괴거동)

  • Choi, Nak-Sam;Kinloch, A.J.
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.22 no.3
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    • pp.611-623
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    • 1998
  • The delamination fracture of multidirectional carbon-fiber/epoxy laminates under the Mode I condition has been studied using the modified beam analysis for a fracture mechanics approach. It was found that the variation of fracture energy $G_IC$ with increasing length of the propagating crack exhibited a minimum for the pure interlaminar fracture and a maximum for the intraply fracture,i.e. a rising "R-curve", which was strongly affected by the degree of fiber bridging and crack-tip splitting arising in the global delamination. The maximum $G_IC$ value was significantly dependent on such types of delamination as no crack jumping, crack jumping into the adjacent ply and edge-delamination. It was shown also that the value of "effective flexural modulus" estimated from the modified beam analysis increased much with the development of fiber bridging behind the crack tip.ehind the crack tip.